This invention relates to new methods for the manufacture from polymer/filler materials of composite substrates such as are used for electric circuits, particularly electronic circuits, and to components for such circuits, which substrates and components can have multiple different electric constants in respective regions thereof, and also relates to articles so manufactured. It also relates to such methods with which at least one of such regions constitutes packaging for the other region or regions.
An important factor in circuit design, especially at the ever higher frequencies and switching speeds that characterize modern designs, is that of the electric properties of the materials used in the manufacture of the substrates and components. For example, the dielectric properties of substrate materials used for microwave transmission media directly impact other key physical properties of the transmission lines. One of the most widely used transmission media at microwave frequencies is that known as xe2x80x9cMicrostripxe2x80x9d. The dielectric constant of Microstrip substrates is a determinant of the width requirement for its conductors, and therefore careful selection of the substrate materials according to their electric properties, particularly their dielectric property values, is crucial to the design, layout, and overall resultant size of such circuits. Typically, the use of higher dielectric materials results in narrower conductor widths, which facilitates overall reduction in size, and this is increasingly important as the trend continues toward miniaturization of such circuits.
Another important problem inherent in electronic circuit design is that of impedance matching, which is one that has been addressed since the earliest days of electronic circuit design, and which usually is required for optimum performance when source and load impedances are unequal. Although many approaches are practiced, the problem has become increasingly challenging in view of the trend towards miniaturization of electronic circuits. This is because prior art methods typically involve the incorporation of extra components within a circuit, requiring additional space. Most commonly the matching is accomplished by inserting matching networks into the circuit between the source and the load. Simple examples might involve the use of an inductance/capacitance circuit to match unequal source and load impedances, or to optimize the gain of an amplifier. Clearly, the addition of such components and/or networks, requiring additional space, significantly hinders miniaturization efforts.
These and other methods of providing impedance matching involve the use of circuit boards that carry a pattern of conductors onto which components are assembled. The creation of these circuit patterns becomes quite complex, and has led to the development of multi-layer circuit boards. Again, the result is one of increased size. Furthermore, the need to select certain components of certain sizes according to their impedance matching abilities limits the overall design flexibility in creating circuits, especially if subsequently one or more components must be replaced with another of different values of electric and physical characteristics.
In addition to careful selection of materials for the circuits and components themselves, the problem of impedance matching must also sometimes be addressed by proper selection of packaging materials. A successful package design, such as for microwave circuits, must meet criteria for impedance matching, low dielectric loss at microwave frequencies, low sensitivity of the dielectric material and conductors to temperature changes, and low capacitance of interconnection to the backside of the ground plane. Therefore, selection of materials according to their electric properties for electronics packaging is yet another important facet for the performance optimization of circuits.
As far as we are aware, there is not currently a method for impedance matching that essentially requires no additional hardware, no additional space, and no constraints on component selection in the circuit designing process. Current impedance matching techniques simply do not provide the needed flexibility and space-saving characteristics.
A major problem resides in the difficulties in choosing a dielectric material that can meet the different requirements of different respective parts of a substrate, a component, or a packaging system, and usually this has required a careful choice on the part of the designer of a single material with which an optimum balance is achieved, accepting that the properties of the material are less suitable for some aspects than would be preferred.
A principal object of the present invention to provide new methods for the manufacture of electric circuit substrates, and of components for such circuits, and of packaging therefor, with which different materials of different dielectric constants can be used successfully in different regions of the substrates, or the components, or the packaging.
Another object is to provide methods for impedance matching in electric circuit substrates, components, and their packaging that are consistent with the current need for circuit miniaturization by reducing, if not eliminating, the need for additional circuitry or additional impedance matching components.
In accordance with the invention there is provided an electric circuit substrate or electric circuit component comprising a body of polymer/filler composite material and having different values of an electric characteristic in different body regions thereof, characterized in that it comprises at least a first body region having a first electric characteristic; and at least a second body region joined to the first region to have a boundary between them, the second body region having a second electric characteristic of value different from that of the same electric characteristic of the first body region.
Also in accordance with the invention there is provided a method of manufacturing an electric circuit substrate or electric circuit component comprising a body of polymer/filler composite material and having different values of an electric characteristic in different body regions thereof, characterized by forming at least a first body region of the polymer/filler composite material having a first electric characteristic; and joining to the first body region a second body region at least one boundary between them by a heat and pressure operation that melts at least polymer at the boundary to effect such joining, the second body region having a second electric characteristic of value different from that of the same electric characteristic of the first body region.